Signal receiver with digital front end supporting multiple band and signal receiving method using the same

ABSTRACT

Disclosed is a method for receiving an analog signal from a receiver supporting at least a first channel band and a second channel band. The method for receiving an analog signal includes sampling the analog signal received through an antenna, generating a decimated signal by passing the sampled signal to a CIC decimation filter; and inputting the decimated signal to a channel selection filter.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C 119(a) to KoreanApplication No. 10-2010-0134104, filed on Dec. 23, 2010, in the KoreanIntellectual Property Office, which is incorporated herein by referencein its entirety set forth in full.

BACKGROUND

Exemplary embodiments of the present invention relate to a digitalreceiver of a mobile communication system of supporting multiplechannels and multiple bands.

Generally, a digital front end serves to perform digital modulation anddemodulation of an RF receiver performing signal processing of a radiofrequency/intermediate frequency (RF/IF) end using digital or discretetime rather than performing the signal processing thereof using ananalog circuit of the related art.

Most of the mobile communication system standards support multiplechannel bands and various frequency bands are supported. As an example,a long term evolution (LTE) system standard supports various frequencybands, such as 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, or thelike.

In the related art, when a single system supports multiple channelbands, a frequency band is narrow so as to all the channel bands insingle hardware architecture and thus, the number of taps required in achannel filter is increased in inverse proportion thereto. In order toimplement the channel filter, a multiplier that is the most complexarithmetic unit in a digital hardware is required. However, the numberof taps is increased and the number of multipliers is also increasedaccordingly, such that complexity in implementing digital hardware maybe increased.

In order to solve the problems, methods for preventing the number ofmultipliers from suddenly increasing by using a multi-stage channelfilter have been used. However, since most of the methods areimplemented by a finite impulse response filter, the methods also have aproblem in that the required number of multipliers is increasedaccording to a channel bands.

The above technology configuration is a background art for helpingunderstanding of the present invention but does not mean the related artwell-known in the art to which the present invention pertains.

SUMMARY

An object of the present invention is to implement a digital front end(DFE) capable of performing digital demodulation of an RF receiver basedon a digital RF technology performing signal processing of an RF/IF endusing digital rather than performing the signal processing thereof usingan analog circuit of the related art.

In particular, exemplary embodiments of the present invention caneffectively process signals according to channel bands without suddenlyincreasing complexity in a system of supporting various channel bands.

The scope of the present invention is not limited to the above-mentionedobjects.

An embodiment of the present invention relates to a method for receivinga signal with a signal receiver with a digital front end supportingmultiple bands, including: sampling signals received through an antennaof the receiver supporting at least a first channel band and a secondchannel band; generating decimated signals by passing the sampled signalto a cascated integrator comb (CIC) decimation filter; inputting thedecimated signal to a channel selection filter.

A first ratio of the first channel band to a first sampling rateincluded in a signal output by passing a first signal having the firstchannel band among the signals to the CIC decimation filter may be equalto a second ratio of the second channel band to a second sampling rateincluded in a signal output by passing a second signal having the secondchannel band among the analog signals to the CIC decimation filter.

The sampling rate at the sampling may be constant regardless of thechannel bands of the analog signals.

The inputting to the channel selection filter may include resampling thedecimated signal.

The step of resampling makes the sampling rate outputted constantregardless of the first channel band and the second channel band.

An embodiment of the present invention relates to a signal receiver witha digital front end supporting multiple bands, including: ananalog-to-digital converter (ADC) sampling an analog signal receivedfrom an antenna with a digital signal; a CIC decimation filterdecimating an output signal from the ADC; and a channel selection filterreceiving a signal output from the CIC decimation filter, wherein theCIC decimation filter has a configuration in which a plurality of thesame CIC filters are connected in series and supports at least a firstchannel band and a second channel band.

A first ratio of the first channel band to a first sampling rateincluded in a signal output by passing a first signal having the firstchannel band among the analog signals to the CIC decimation filter maybe equal to a second ratio of the second channel band to a secondsampling rate included in a signal output by passing a second signalhaving the second channel band among the analog signals to the CICdecimation filter.

The sampling rate of the ADC may be constant regardless of the channelbands of the analog signals.

A resampler making the sampling rate output regardless of the firstchannel band and the second channel band constant may be furtherprovided between the CIC decimation filter and the channel selectionfilter.

A CIC compensation filter may be further provided between the CICdecimation filter and the resampler and a frequency response of the CICcompensation filter at the first channel band and the second channelband has an inverse relationship with a frequency response of the CICdecimation filter at the first channel band and the second channel band.

As set forth above, the exemplary embodiments of the present inventioncan effectively support the system of supporting various channel bandsand frequency bands by variably controlling the integer or realdecimation rate according to the channel bands or frequency bands of thesignal in the digital front end.

In addition, the exemplary embodiments of the present invention canreduce the power consumption while reducing the complexity of hardwareconfiguration by minimizing the number of multipliers.

The scope of the present invention is not limited to the above-mentionedeffects.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages will be moreclearly understood from the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing a schematic structure of a digital front endaccording to an exemplary embodiment of the present invention;

FIG. 2 is a diagram showing a structure of a CIC decimation filter in adigital front end according to the exemplary embodiment of the presentinvention;

FIG. 3 is a diagram showing a structure of a multi-stage CIC decimationfilter supporting multiple bands based on an LTE system;

FIG. 4 is a diagram for explaining a structure of a CIC compensationfilter according to the exemplary embodiment of the present invention;

FIG. 5 is a diagram for explaining a structure of a channel compensationfilter according to the exemplary embodiment of the present invention;and

FIG. 6 is a diagram showing a schematic structure of the digital frontend including a DC offset compensation block and an IQ mismatchcompensation block according to the exemplary embodiment of the presentinvention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to accompanying drawings. However, the embodiments are forillustrative purposes only and are not intended to limit the scope ofthe invention.

In describing the embodiment, a thickness of lines illustrated in thedrawings, a size of components, etc., may be exaggeratedly illustratedfor clearness and convenience of explanation. In addition, termsdescribed to be below are terms defined in consideration of functions inthe present invention, which may be changed according to the intentionor practice of a user or an operator. Therefore, these terms will bedefined based on contents throughout the specification.

Exemplary embodiments of the present invention will describe anoperation structure of a digital receiver supporting multiple channelbands in a radio communication system. A case of using 6 frequency bands(1 MHz, 4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz) supported in anLTE system standard as an input will be described below, but a case ofusing other frequency bands may also be applied.

FIG. 1 is a diagram for explaining a schematic structure of a digitalfront end according to an exemplary embodiment of the present invention.

An RF input signal is input to a digital front end via a low noiseamplifier (LNA) and an analog to digital converter (ADC). In theexemplary embodiments of the present invention, the digital front endserves to convert a signal, which is converted into digital, into asampling rate required in a standard of a system through a decimationand filtering process.

Referring to FIG. 1, a digital front end (DFE) 100 according to theexemplary embodiment of the present invention includes a CIC decimationfilter 110, a CIC compensation filter 120, a resampler 130, and achannel selection filter 140.

The CIC decimation filter 110 serves to lower sampling rates of receivedsignals so as to prevent the received signals from being processed withlarge oversampling rate in the remaining blocks of a DFE block.

The exemplary embodiment of the present invention may design the CICdecimation filter at multi-stage in the case of a system of supportingmultiple bands so as to constantly maintain a ratio of a sampling rateto a channel band. By the configuration, the exemplary embodiment of thepresent invention can effectively filter even a signal having a narrowband without increasing the number of multipliers in a channel selectionfilter.

The CIC compensation filter 120 serves to compensate in-band error thatoccurs in the CIC decimation filter 110.

One of characteristics included in the digital RF receiver is changeddepending on a frequency of a local oscillator (LO) signal rather thandepending on the sampling rates of the received signals.

Although data rates of the received signals are the same, the samplingrates of the sampled received signals may be changed when an LO signalfrequency of a communication channel is different.

Therefore, the sampling rates of the received signals that are madethrough the signal processing needs to be constant. This is made throughthe resampler 130 block. The multiple bands may be supported by theoperation of the resampler block.

The channel selection filter 140, which is a filter performing verysudden filtering at an edge of a channel frequency band, serves toremove signal out-of-band noise. Further, the ratios of sampling ratesto bands are not changed according to the channels through the resampler130 block and thus, the channel selection filter 140 positioned at thelatter part may be more effectively implemented.

FIG. 2 is a diagram for explaining the CIC decimation filter 110 in theDFE according to the exemplary embodiment of the present invention.

The CIC decimation filter 110 serves to receive an ADC output signal andfilter and decimate the received ADC output signal. Since the sampledsignal of the ADC is the fastest signal among signals in the DFE 100block, a structure of the decimation filter 110 is also simple.Therefore, in the exemplary embodiment of the present invention, thedecimation filter is implemented using a CIC filter without a multiplierinstead of a general digital low pass filter that needs a multiplier.

$\begin{matrix}{y_{k} = {\frac{1}{N}{\sum\limits_{j = {k - {({N - 1})}}}^{k}x_{j}}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

It can be appreciated from Equation 1 that a filter coefficientmultiplied by input x is 1. Therefore, since the multiplier is notneeded in implementing the CIC filter, complexity in implementinghardware can be reduced.

The number of non-zero impulses is an order of the CIC filter.Generally, the CIC filter needs to be an integer multiple of N so as toperform down sampling by N. As described above, only when the order ofthe CIC filter is an integer multiple of the down sampling, an aliasingproblem occurring by an interference signal existing at adjacentchannels during the down sampling process may be solved. However, alarge interference signal above several tens of dB may not be filteredby only a single CIC filter. As a result, a multiple filtering effectmay be obtained by connecting the same CIC filters 211, 212, and 213 inseries, such that an overlapping problem of the signal generated by thedown sampling process and the interference signal may be solved.

Further, even when a single system supports the multiple channel bands,the CIC filter may effectively change the channel filter according tothe channel band without greatly increasing the complexity. When asignal having a narrow frequency band has a constant ADC output samplingrate, the number of taps of the channel selection filter for the signalhaving a narrow frequency signal is suddenly increased and themultipliers are needed accordingly, if the signal having a narrowfrequency band passes through the CIC decimation filter using all thesame sampling rates in each channel band. The multiplier is one ofarithmetic units having large complexity. As a result, when the numberof multipliers is increased, the complexity in implementing hardware isincreased. Accordingly, in order to prevent the number of multipliersfrom increasing in the exemplary embodiment of the present invention,the CIC decimation filters 210, 220, 230, and 240 are implemented bymulti-stage, such that the number of taps of the channel selectionfilter is not increased and the CIC filter does not use the multiplier,such that the CIC filter may effectively filter even the signal having anarrow frequency band without greatly increasing the complexity.

FIG. 3 is a diagram for explaining the CIC decimation filter 110 in theDFE according to the exemplary embodiment of the present invention.

FIG. 3 shows the multi-stage CIC decimation filter supporting themultiple bands defined in the LTE system.

Table 1 shows a modem input sampling rate according to the input signalband in the LTE system. It can be appreciated that the ratios of thesampling rates to the bands are the same in all the bands. Therefore,the CIC decimation filter performs the multi-stage decimation accordingto bands to control the output sampling rate of the signal, such thatthe number of resampler 130 blocks of the latter end may be equal to thenumber of taps of the channel selection filter.

TABLE 1 Band(MHz) Sampling Rate Required in Standard(MHz) 20 30.72 1523.04 10 15.36 5 7.68 3 3.84 1.4 1.92

Referring to FIG. 3, the sampling rate of the signal is controlled whilethe multi-stage CIC decimation filter 110 is operated according to thefrequency band of the input signal.

For example, when the ADC output sampling rate is 275 MHz and a band is20 MHz, only a first CIC filter 310 and a down sampling block by 2 311are operated to generate an output sampling rate of 137.5 MHz.

When the band of the input signal is 10 MHz, the first CIC filter 310, asecond CIC filter 312, and two down sampling blocks by 2 311 and 313 areoperated to generate an output sampling rate of 68.75 MHz. Even when thebands of the input signals are 5 MHz, 3 MHz, and 1.4 MHz, the CICfilters and the down sampling blocks by 2 each corresponding to thebands are operated like the above-mentioned process to generate outputsampling rates of 34.375 MHz, 17.1875 MHz, 8.5938 MHz, respectively.

Table 2 shows the output sampling rates of the signal passing throughthe multi-stage CIC decimation filter 110 according to the exemplaryembodiment of the present invention depending on the frequency bands.

TABLE 2 CIC Output Sampling Rate CIC Output Sampling Band of InputSampling Rate Required in Rate/Sampling Rate Signal(MHz) (MHz)Standard(MHz) Required in Standard 20 137.5 30.72 4.476 15 137.5 23.045.968 10 68.75 15.36 4.476 5 34.375 7.68 4.476 3 17.1875 3.84 4.476 1.48.5938 1.92 4.476

As can be appreciated from Table 2, the decimation rates to be processedafter the CIC decimation filter 110 are the same in all the bands otherthan 15 MHz. Accordingly, the problem in that the number of multipliersis additionally increased according to the band in the resampler 130 andthe channel selection filter 140 is solved by using the multi-stage CICdecimation filter 110. The number of CIC filters may be increasedaccording to the bands, but the CIC filter has a structure that does notinclude the multiplier, such that the complexity of the hardwareconfiguration is not greatly increased.

FIG. 4 is a diagram for explaining an operation of the CIC compensationfilter 120 according to the exemplary embodiment of the presentinvention.

The CIC compensation filter 120 is a block compensating distortionsoccurring in the CIC decimation filter 110. The CIC filter does notinclude a flat pass band, thereby causing a phenomenon that an in-bandsignal is distorted. An FIR filter that is a reciprocal number of theCIC filter provided so as to compensate the distortion may be referredto the CIC compensation filter 120. The CIC compensation filter 120 usesthe FIR filter having the multiplier, but is operated at the samplingrate lower than that of the CIC decimation filter 110, such that thehardware configuration of the CIC compensation filter 120 may be moreefficiently implemented. In addition, the CIC compensation filter 120has a filtering function for adjacent channels and therefore, may alsoinclude a function of preventing the aliasing occurring when the downsampling is performed in the resampler 130 of the latter end.

CIC compensation filters 410 and 420 described in FIG. 4 are operated asvalues of different filter coefficients according to the input bands.However, according to Table 2, when the multi-stage CIC filter accordingto the frequency band is used in the LTE system, the ratios of [CICoutput sampling rate/sampling rate required in standard] are the sameexcept for the case of 15 MHz, such that the same CIC compensationfilter 410 may be used for the above-mentioned five frequency bands.When the ratios of [CIC output sampling rate/sampling rate required instandard] even for the system supporting various bands rather than theLTE system are the same, a single filter may be used, such that thenumber of filter coefficients to be stored is reduced, therebyincreasing the efficiency of the hardware implementation.

In addition, the use of the CIC compensation filter 120 is fluidaccording to the corresponding system. For example, in the case of theLTE system of which carrier spacing is about 15 kHz, the influence ofdistortions due to the CIC decimation filter is large and thus, the CICcompensation filter 120 is required. On the other hand, in the case of aDVB-H system of which carrier spacing is not 5 kHz, the influence ofdistortions due to the CIC decimation filter 110 is not large and thus,a separate CIC compensation filter 120 may not be required. In thiscase, a function of preventing the aliasing from occurring when the downsampling is performed in the resampler 130 through a simple low passfilter (LPF) instead of the CIC decimation filter 110 may be added.

The resampler 130 block is a block that generates an output signalhaving a resampling rate set using the sampled input signal. The basicdecimation filter performs an integer decimation function, while theresampler block performs a real decimation function. As a result, theresampler needs a function of estimating the output signal from thegiven input signal. The resampler used in the exemplary embodiment ofthe present invention uses a Farrow filter to which Lagrangeinterpolator polynomial is applied, thereby effectively estimating theoutput signal with a small number of taps.

Equation 2 is an equation that represents the Lagrange interpolatorpolynomial and the resampling. In Equation 2, t does not mean continuoustime t, but is a value representing a position to be resampled as arelative position within 1 symbol interval.

$\begin{matrix}{{{y(t)} = {\sum\limits_{i = I_{1}}^{I_{2}}{C_{i}{x\left( {I_{1} + I_{2} - i} \right)}\mspace{14mu} {where}}}}{C_{i} = {\prod\limits_{{j = I_{1}},{j \neq i}}^{I_{2}}\; \frac{t - t_{j}}{t_{i} - t_{j}}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

When using the resampler 130 using the Farrow filter, any input signalmay be output by generating the desired sampling rates. Even when theinput sampling rate is fluid, the constant output sampling rate isgenerated through the resampler 130, which may be effectively used inthe system supporting the multiple bands.

FIG. 5 is a diagram for explaining an operation of the channel selectionfilter 140 according to the exemplary embodiment of the presentinvention.

The channel selection filter 140, which is a filter performing verysudden filtering at an edge of a channel frequency band, serves toremove signal out-of-band noise. The channel selection filter 140according to the exemplary embodiment of the present invention may beefficiently implemented in hardware without increasing the multipliersince the ratios of the sampling rates to the channel bands of all thesignals are the same and the same number of taps is used regardless ofthe bands or the channel bands, due to the operation of the CICdecimation filter 110 and the resampler 130 of the front end. Channelselection filters 510 and 520 described in FIG. 5 store the coefficientsof the channel selection filter according to each of the frequencybands. However, the channel selection filters 510 and 520 may also beimplemented with one filter coefficient when the ratios of the samplingrates to the frequency bands are the same. In the case of the LTEsystem, the remaining five bands other than a band of 3 MHz may beimplemented with one filter coefficient.

Table 3 shows the output sampling rate in each block according to thedigital front end operation in the exemplary embodiment of the presentinvention.

TABLE 3 ADC Output CIC Decimation Resampler Channel Selection SamplingOutput Output Filter Output Band Rate CIC Sampling Sampling RateSampling (MHz) (MHz) Decimation Rate(MHz) Resampling (MHz) Rate(MHz) 20275 2 137.5 2.2380 30.72*2 30.72*2 15 275 2 137.5 2.9839 23.04*2 23.04*210 275 4 68.75 2.2380 15.36*2 15.36*2 5 275 8 34.375 2.2380  7.68*2 7.68*2 3 275 16 17.1875 2.2380  3.84*2  3.84*2 1.4 275 32 8.5938 2.2380 1.92*2  1.92*2

Table 3 shows an example when the LTE system supporting six bands hasthe ADC output sampling rate of 275 MHz. As can be appreciated in Table3, the CIC decimation filter 110 is configured by multi-stage, such thatthe resampling rates applied according to each band are approximatelythe same and the ratios of the sampling rates required in a basebandmodem to the sampling rates of the output from the channel selectionfilter 140 are the same, such that the same channel selection filter 140may be used.

FIG. 6 is a diagram for explaining a digital front end 600 including aDC offset compensation block 630 and an IQ mismatch compensation filter640. In the exemplary embodiment of the present invention, since thedigital front end 600 may output the desired sampling rate through theresampler 130 block and thus, be operated even in a Zero IF structurethat does not permit IF. In the Zero IF structure, a separate mixer isnot required. However, the DC offset or the IQ mismatch may occur in astructure without the mixer and as a result, the separate DC offsetcompensation block 630 and IQ mismatch compensation block 640 may berequired.

The DC offset compensation block 630 serves to estimate and remove theDC offset that may be present in the received signal due to the receiverand noise.

$\begin{matrix}{{{estimated}\mspace{14mu} {DC}\mspace{11mu} {offset}} = {\frac{1}{N}{\sum\limits_{k = s}^{s + {({N - 1})}}{r(k)}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Equation 3, which represents the estimation of DC offset of the receivedsignal in the DC offset compensation block 630 used in the exemplaryembodiment of the present invention, uses an average process of thereceived signal during the set number of samples.

The signal passing through the DC offset compensation block 630 passesthrough the IQ mismatch compensation block 640. Characteristics of Ichannel and Q channel of the digital RF receiver may be different in thestructure that does not use the mixer. This phenomenon distorts an Ichannel signal and an Q channel signal, in particular, deteriorates animage rejection rate. In the exemplary embodiment of the presentinvention, a method for estimating and compensating the I/Q mismatchdegree based on a condition in which the I channel and Q channelreceived signals need to be satisfied is used.

Equation 4 represents a condition in which a signal needs to besatisfied when there is no gain mismatch between the I channel and the Qchannel. Based on the condition, the gain mismatch between the I channeland the Q channel may be estimated through Equation 5.

$\begin{matrix}{{E\left\{ x_{I}^{2} \right\}} = {E\left\{ x_{Q}^{2} \right\}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack \\{{{Estimated}\mspace{14mu} {gain}\mspace{14mu} {mismatch}} = \frac{\sqrt{E\left\{ x_{Q}^{2} \right\}} - \sqrt{E\left\{ x_{I}^{2} \right\}}}{\sqrt{E\left\{ x_{Q}^{2} \right\}} + \sqrt{E\left\{ x_{I}^{2} \right\}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Meanwhile, Equations 6 and 7 represent a condition in which the signalneeds to be satisfied when there is no phase mismatch between the Ichannel and the Q channel and equations of estimating the phase mismatchbetween the I channel and the Q channel based on the condition.

$\begin{matrix}{{E\left\{ {x_{I}x_{Q}} \right\}} = 0} & \left\lbrack {{Equation}\mspace{20mu} 6} \right\rbrack \\{{{Estimated}\mspace{14mu} {phase}\mspace{14mu} {mismatch}} = {- {\sin^{- 1}\left( \frac{2E\left\{ {x_{1}x_{Q}} \right\}}{{E\left\{ x_{I}^{2} \right\}} + {E\left\{ x_{Q}^{2} \right\}}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

Hereinafter, a method for receiving analog signals according to theexemplary embodiment of the present invention will be described.

In this case, the analog signals may be a radio high frequencycommunication signal. The method may be performed in the receiverincluding the above-mentioned digital front end.

The method is a method for receiving analog signals in the receiversupporting a first channel band and a second channel band. Accordingly,the receiver may additionally support a third channel band in somecases. The first channel band and the second channel band may eachinclude bands shown in Tables 1 to 3.

The receiving method may include sampling analog signals receivedthrough an antenna, generating decimated signals by passing the sampledsignal to the CIC decimation filter 110, and inputting the decimatedsignals to the channel selection filter 140. In this case, anotherdigital processing block may be further included between the CICdecimation filter 110 and the channel selection filter 140, ifnecessary. The digital processing block may include the CIC compensationfilter 120, the resampler 130, or the like, as described above. Herein,the sampling may be performed by the ADC.

In this case, a first ratio of the first channel band to the firstsampling rate included in the signal output by passing a first signalhaving the first channel band among the analog signals to the CICdecimation filter 110 may be equal to a second ratio of the secondchannel band to the second sampling rate included in the signal outputby passing the second signal having the second channel band among theanalog signals to the CIC decimation filter 110. For example, the firstchannel band, the first sampling rate, the second channel band, and thesecond sampling rate may each be a band having 20 MHz, 137.5 MHz, a bandhaving 10 MHz, and 68.75 MHz that are shown in Table 3. In this case,both of the first ratio and the second ratio may be 6.875.

In this case, the sampling rate at the sampling may be constantregardless of the channel bands of the analog signals. That is, thesampling rate of the ADC may be, for example, 275 MHz at all times.

In this case, the inputting to the channel selection filter 140 mayinclude resampling the decimated signals. The resampling may beperformed by the resampler 140.

The resampler 140 serves to make the resampling rate output regardlessof the channel bands constant.

Hereinafter, an analog signal receiver according to another exemplaryembodiment of the present invention will be described. The analog signalreceiver, which is a receiver having the above-mentioned digital frontend, may receive and process the analog signal inputted to the antenna.

The analog signal receiver may support at least the first channel bandand the second channel band. Accordingly, the analog signal receiver mayadditionally support the third channel band in some cases. The firstchannel band and the second channel band may each include the bandsshown in Tables 1 to 3.

The analog signal receiver may include the analog-to digital converter(ADC) that samples the analog signals received from the antenna with thedigital signals, the CIC decimation filter 110 that decimates the outputsignals from the ADC, and the channel selection filter 140 that receivesthe signals output from the CIC decimation filter 110, wherein the CICdecimation filter 110 may have a configuration in which a plurality ofthe same CIC filters 210, 220, 230, and 240 are connected in series Inthis case, another digital processing block may be further includedbetween the CIC decimation filter 110 and the channel selection filter140, if necessary.

In this case, a first ratio of the first channel band to the firstsampling rate included in the signal output by passing a first signalhaving the first channel band among the analog signals to the CICdecimation filter 110 may be equal to a second ratio of the secondchannel band to the second sampling rate included in the signal outputby passing the second signal having the second channel band among theanalog signals to the CIC decimation filter 110. For example, the firstchannel band, the first sampling rate, the second channel band, and thesecond sampling rate may each be a band having 20 MHz, 137.5 MHz, a bandhaving 10 MHz, and 68.75 MHz that are shown in Table 3. In this case,both of the first ratio and the second ratio may be 6.875.

In this case, the sampling rate of the ADC may be constant regardless ofthe channel bands of the analog signals. That is, the sampling rate ofthe ADC may be, for example, 275 MHz at all times. Further, the firstresampling rate to the first signal having the first channel band amongthe analog signals may be equal to the second resampling rate to thesecond signal having the second channel band among the analog signals.

In this case, the analog signal receiver may further include theresampler 130 between the CIC decimation filter 110 and the channelselection filter 140.

In this case, the CIC compensation filter 120 may be further includedbetween the CIC decimation filter 110 and the resampler 130 and thefrequency response of the CIC compensation filter 120 at the firstchannel band and the second channel band may have the inverserelationship with the frequency response of the CIC decimation filter110 at the first channel band and the second channel band.

Each component of the exemplary embodiment of the present invention maybe implemented by a programmable logic gate array (FPGA) or a dedicatedsemiconductor device such as ASIC. Further, each component mayseparately be implemented in different semiconductor chips, but severalcomponents of the exemplary embodiment of the present invention may beimplemented on a single semiconductor chip.

The embodiments of the present invention have been disclosed above forillustrative purposes. Those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

1. A method for receiving a signal with a signal receiver with a digitalfront end supporting multiple bands, comprising: sampling analog signalsreceived through an antenna of the receiver supporting at least a firstchannel band and a second channel band; generating decimated signals bypassing the sampled signal to a CIC decimation filter; inputting thedecimated signal to a channel selection filter.
 2. The method of claim1, wherein a first ratio of the first channel band to a first samplingrate included in a signal output by passing a first signal having thefirst channel band among the analog signals to the CIC decimation filteris equal to a second ratio of the second channel band to a secondsampling rate included in a signal output by passing a second signalhaving the second channel band among the analog signals to the CICdecimation filter.
 3. The method of claim 2, wherein the sampling rateat the step of sampling is constant regardless of the channel bands ofthe analog signals.
 4. The method of claim 1, wherein the step ofinputting to the channel selection filter includes resampling thedecimated signal.
 5. The method of claim 4, wherein the step ofresampling makes the sampling rate outputted constant regardless of thefirst channel band and the second channel band.
 6. A signal receiverwith a digital front end supporting multiple bands, comprising: ananalog-to-digital converter (ADC) configured to sample an analog signalreceived from an antenna with a digital signal; a CIC decimation filterconfigured to decimate an output signal from the ADC; and a channelselection filter configured to receive a signal output from the CICdecimation filter, wherein the CIC decimation filter has a configurationin which a plurality of the same CIC filters are connected in series andsupports at least a first channel band and a second channel band.
 7. Thesignal receiver of claim 6, wherein a first ratio of the first channelband to a first sampling rate included in a signal output by passing afirst signal having the first channel band among the analog signals tothe CIC decimation filter is equal to a second ratio of the secondchannel band to a second sampling rate included in a signal output bypassing a second signal having the second channel band among the analogsignals to the CIC decimation filter.
 8. The signal receiver of claim 7,wherein the sampling rate of the ADC is constant regardless of thechannel bands of the analog signals.
 9. The signal receiver of claim 6,wherein a resampler making the sampling rate outputted constantregardless of the first channel band and the second channel band isfurther provided between the CIC decimation filter and the channelselection filter.
 10. The receiver of claim 9, wherein a CICcompensation filter is further provided between the CIC decimationfilter and the resampler, and a frequency response of the CICcompensation filter at the first channel band and the second channelband has an inverse relationship with a frequency response of the CICdecimation filter at the first channel band and the second channel band.